Immodest perturbation

Incurious and Unread in this comment talked about a “modest perturbation” and positive and negative feedbacks:

I can’t help feel that Gaia is letting us down here. It seems that we keep on getting positive feedback effects on the climate rather than negative feedback.

That seems kind of odd. As I understand it, the climate has been fairly stable pre-AGW, which suggests that negative feedback effects dominated. We have what seems to me (probably in my ignorance) a modest perturbation and suddenly we are envisaging positive feedback and an uncontrollable excursion to a new Venusian equilibrium.

Is it just that it is the positive feedback stories which hit the headlines, or is there some underlying reason why there are more positive feedback than negative feedback effects?

First up, it’s forcings that change the temperature positively or negatively. Forcings are amplified by feedbacks, positive and negative. For a stable climate the net effect of forcings and feedbacks should be zero, they should cancel each other out.

The following graph shows the main radiative forcings:

Figure 1: Radiative forcings

CO2 is about equivalent to the net human forcing. The others cancel each other out.

As an aside, cloud effects seem to me to be a feedback rather than a forcing, and may turn out to be mildly positive. If so this is not good news.

Now have a look at this graph where CO2 is plotted against temperature for the last 800,000 years:

Figure 2: Temperature and CO2 records

CO2 has varied from about 180 to 280 ppm to give us successive ice ages. Notice the current level of COI2 on the right. Distinctly immodest in that context.

Now have a look at this article which tells us that current CO2 levels are higher than they have been for 15 million years. That’s quite a perturbation in the space of about 150 years, although most of the increase has come since WW2.

This graph tells the story of the up-tick from the 1950s.

Figure 3: CO2 since 1750

This one tells the story of the Holocene. Again distinctly immodest in recent times.

Figure 4: CO2 over the last 8000 years

In his Idaho Testimony (Fig. 11) James Hansen tells us that in the Cenozoic era natural CO2 forcing was at the rate of 100 ppm/My (0.0001 per year) as against 2 per year now. Again somewhat immodest. A mere 20,000 times as much. This image shows us how such a mild rate of forcing has moved the temperatures over the last 65 million years.

Figure 5: Cenozoic era climate change

Note where the temperature was 15 million years ago. Of course the wild swings of the last 3 million years have been primarily caused by orbital changes, a function of when the major ice sheets are engaged in the system in a particular temperature band, but that’s another story.

The effect of forcings and feedbacks on temperature is normally expressed in terms of watts par square metre. These graphs from Hansen at NASA show the current forcing at 3 watts per square metre of GHGs plotted against various phenomena:

Figure 6: Climate forcings over 450 kyr

If you follow the red line in the middle graph you get the impression that something big is going to happen. You can see in the third graph that the temperature beast is stirring. Remember that the long term feedbacks such as the ice sheet response take centuries to work their way through the system.

BTW, those graphs are from a few years back. I think the 3 watts forcing refers to short term Charney-type feedbacks.

The net forcings and feedbacks appear to translate into temperature at the rate of 0.75C for each watt per square metre. The direct effect of CO2 is actually quite small, but this is amplified through feedbacks. One of the main ones is water vapour. Warmer air carries more water vapour which in turn traps more radiation, which warms the air which… It must be a diminishing effect, because the end result is equilibrium rather than a runaway effect. One source gives the effect of water vapour as 1.8 watts per square metre of energy trapped for each extra C of temperature.

You will recall this image in the previous post:

Figure 7: Long-term climate sensitivity

So that image is based on the notion that the direct forcings give you 1C, amplified by short term feedbacks to 3C and longer term feedbacks to 6C. If along the way you trip off something like releasing methane from the permafrost, of fry the Amazon and other tropical forests, then be very afraid.

There is an account of forcings and climate sensitivity in Hansen’s Bjerknes Lecture. Go here and download the pdf from 20 December, 2008.

In that lecture he also addresses the possibility of a Venus effect. He thinks the Venus effect is possible if we burn all the coal in the ground. If we burn all the carbon available in tar sands he sees a Venus effect as a “dead certainty”.

So the take-out of this story is that what we’ve done in the last 100 years or so is anything but modest. A mere 100 ppm is equivalent to about 2 million years of natural change during the bulk of the Cenozoic. That’s apart from the Paleocene–Eocene Thermal Maximum (PETM) 55 myr ago, shown as a blip on Figure 5 above, where the temperature rose 6C over 20,000 years and then returned to normal for those times over 120,000 to 170,000 years. That’s fast in geologic time. But the perturbation we have caused and would cause under BAU in a few short centuries is thought to be of a similar order in terms of tonnes of carbon emitted into the atmosphere. That’s a blitzkrieg on the climate system.

In these circumstances Gaia is pushed rudely aside. But be warned, she will have the last word.

BTW Hansen thinks that Gaia as a factor that intentionally steers the system towards conditions suitable for life is basically rubbish. The earth system doesn’t care whether we turn into a Venus-like planet.

The is another perspective which says that conditions for life are really quite fragile and operate within a small band at the margin.

Without the greenhouse effect the average earth temperature would be about -18C, fluctuating madly on a daily basis. This is really quite warm on the average if you consider that’s 255 Kelvin. The greenhouse gases, a minuscule fraction of the atmosphere, which itself is like a coat of paint on a basket ball, give us an extra 32C or so and equalises the temperature across the 24 hours and the seasons.

Under present conditions we have a balance of about 340 watts per square metre in and roughly the same out. But a gap of a few watts has opened up because we are messing with a trace gas that represents about one 2500th of the atmosphere.

Some sceptics say that’s too small to have an effect. Is it? Every evening I take a one mg pill which helps me sleep at nights. It’s because I have a somewhat obsessive personality that leads my to write posts like this. In terms of my body weight that works out at one in 72 million. Seems to work OK.

A few watts on top of 340 adds a few degrees on top of 287 Kelvin and civilisation is kaputt!

So we best be careful how we mess with the earth system. Gaia if she exists doesn’t care what happens to us. We will be the authors of our own destiny.

55 thoughts on “Immodest perturbation”

  1. Brian,

    Thanks for the post and for attempting to answer my question. I will take some time to read it carefully.

    However, can I just say that my use of the term “modest” was with respect to the absolutes of the earth’s climate and the greenhouse effect rather than relative to climate history. (You have shown conclusively that it is far from modest in the latter context).

    For example, your graph shows forcings of around 3W/m2 which can be compared to total solar radiation of 340MW/m2: ie around 1%.

    Now, if you were driving your car and increased the gas by 1%, you wouldn’t expect your engine to explode. Rather, your car would speed up by 1% (or 0.5% is it?). Obviously, a car engine is designed to have lots of negative feedback to ensure its performance is stable.

    The earth’s climate engine is not designed, but that does not mean, a priori, that it is not stable. It has been stable in the past to forcing variations of similar magnitudes, so why is it not stable now? Your analysis shows that the rate of change of forcing is much, much faster than historical rates, so perhaps that suggests where the answer might lie.

  2. Yes, as someone who has followed this since university days* what we have learned is that this is an incredibly sensitive system.

    Though the last 3M years or so have been a (in the sense of regularity) stable glacial/inter glacial cycle (probably because of the current geological configuration), prior to that the Earth has gone through some massive climate changes, from extremely hot to extremely cold. Which gives some indication of how powerful the feedback mechanisms can be.

    We are living through the greatest experiment humanity has ever undertaken, with potential risks that include extinction. All those ‘climate deniers’ must be very gutsy (or selfish of course) people.

    Then again, those who advocate wasting precious fossil fuels by burning them for electricity already demonstrate their disdain for future generations. If you are happy to starve them of chemicals, plastics, etc then why worry about them boiling/starving/flooding/etc.

    * Though back in those days most tended to discount any major climate impacts mainly because no one realised how sensitive the climate was, plus no one really thought we’d still be burning coal (and in such quantities). If you had asked me at 11 years of age whether we’d still burning coal for electricity now, I’d have laughed at you, even at that age I didn’t think anyone could be that stupid.

  3. IU @ 1, the climate system is actually quite unstable, I think, as we experience it, based for example on Figures 2, 5 and 6 above. Moreover each single degree from here on is likely to produce something like 15 metres sea level rise or more. In terms of human settlement that’s huge. When you consider that the oceans are an average of 3.6 km deep it’s trivial.

  4. Brian,

    excellent summary. I&U – your car example is a false analogy. You’re anchoring a 1% change in the wrong context.

    Zero speed in your car, applied to Earth would have us at moon temperature, because it is the atmosphere that warms. So complex life lives in the 80-110 km zone, and really thrives in a much narrower band than that (say about 10 kmh). So it’s not 1% of the total, it’s much greater. And, as you say, the forcing is much faster. External forcing in normal conditions is very slow, internal feedbacks are much faster (Big natural fast external forcings are geologically rare). Humans have provided a rapid external (to natural processes) forcing. Perturb any complex system quickly and you will exercise more feedbacks than you would perturbing it slowly.

    Think of a sand pile dropping a grain on at a time. You will produce many small slides and the occasional avalanche (in a power law distribution). Repeat using a bucket of sand at a time. More large avalanches, many more small ones.

    Nothing modest there at all.

  5. Brian @3,

    I think we are a little bit at cross purposes. Suppose, as Hansen asserts, that a doubling of CO2 leads to a temperature increase of 3C and, further, suppose that lower or higher CO2 increases lead to proportionately lower or higher temperature increases. That, to me, is a “stable” climate, just like engine performance is stable if changes to the throttling lead to proportionate changes in power.

    What I was getting at was the potential for disproportionate changes. In the Hansen lecture you link to he notes:

    What is different about the human-made forcing is the rapidity at which we are increasing it, on the time scale of a century or a few centuries. It does not provide enough time for negative feedbacks, such as changes in the weathering rate, to be a major factor.

    That is the sort of answer I was looking for.

    That is not to say that the proportionate changes are something that we should be willing to endure. As you note, these changes alone can be catastrophic.

  6. Thank you Brian for taking this up so fully (and I&U for asking the question). Feedbacks and how the models cope with them is the absolutely critical question in judging how “settled” the science actually is.

    There is of course the paper from Lindzen and Choi 18 months ago which put the net feedbacks (climate sensitivity) at 6 times lower than the IPCC best estimate. Yes, this paper has been criticised (and defended), but the criticisms themselves have highlighted how difficult the feedback problem is, and the simplistic ways in which the current climate models deal with it. Any assumption that we are saturating the negative feedbacks, and that positive feedbacks will determine the future, is just that.

    The only thing of course that will unequivocally establish net feedback is future temperature. We rely currently on computer modelling. Real science is based on empirical observation. The point that, if there is a problem of the size that some predict, we cannot wait for the empirical observations to be in before taking action is a valid one. But so is the point about the difference between real science and computer modelling. I know I am something of a stuck record on this but I am convinced that many commenters here without a scientific background – and that seems to be the majority of them – don’t comprehend the importance of it.

    And to the extent that there are empirical observations of the metric central to the public debate (mistakenly, because average global temperature is an entirely artificial and grossly simplified construct, but let’s pretend it matters), for the past decade warming as measured by global temperature average has been well below the rate the models predict. Right now – January-February 2011 – the anomaly from the thirty year average is actually negative (I am surprised – irony alert – that Climate Clippings have never mentioned this rather interesting fact).

    OK don’t tell me about short time spans in climate terms or La Ninas, I agree that this does not actually prove anything about feedbacks, but it is becoming at least suggestive. It is certainly more valid to suggest that ten years, or even two months, of world-wide data might be meaningful, than it is to suggest that a bit of flooding in some regions of one country says something meaningful about global warming, as certain people continue to claim. (I will pass over the ludicrous opportunistic attempts by a few to link an earthquake-generated tsunami to climate change.)

    I repeat: I am not holding this up as any kind of definitive proof of anything. All I am saying is that feedback is a known unknown, It is so unknown that it is highly unlikely that current “official” (I try to avoid words like denier or alarmist) estimates are anywhere near right, and it is at least arguable that the balance of probabilities is that they err, perhaps significantly, on the high side.

  7. Wozza’s ghost, this “real science is not computer modelling” line is a dishonest furphy, because a) all science is about testing predictions,i.e. the models come before the experiments, whether they’re computer-based models or thought experiments and b) climate science involves a lot of experiments. Which happen to meet the predictions of the models, quite often.

    Try telling an aerospace engineer that “real science is not computer modelling.” Or Einstein, for that matter. The idea is ridiculous.

  8. I&U @6

    Hansen also asserted of course, in 1986, that the first decade of the 21st century alone would see a warming of between 2 and 4 degrees (F). But of course he will be right this time.

    OK, sorry, not central to the topic, but I couldn’t resist. And the credibility of some of those whose views a few here seem to think are cast as infallible in tablets of stone is at least peripherally relevant.

  9. sg I am not saying that modelling is not useful. I am saying that it does not produce empirical observations. This may be obvious to you and me, but some seem confused.

    The way the IPCC does its modelling exacerbates the problem too, but let’s not start a thread hijack.

  10. I&U @6,

    The “stability” issue you are exploring becomes less likely in a heavily perturbed system. Venus is stable now, but has been very different in the past.

    One important issue has nothing to do with humans and asks why Earth is in an ice-age with oscillating glacial and interglacial climates (i.e. relatively unstable at present). It’s due to the orientation of the continents, a circumpolar vortex that provides an ice cap plus the Tibetan Plateau (high albedo at low latitudes)combined with reduced CO2 (these are interrelated).

    The past 2.5 million years is a period of relative instability. However, the amount of human-induced forcing to date and to come is still a major event in Earth’s geological history regardless of the starting point.

    One fundamental property of complex self-adaptating systems are feedbacks that will oscillate due to internal and external forcing. The same properties that make them self-adapting, also produce large perturbations if subject to rapid changes in energy inputs. Positive feedback processes are a key part of what makes complex systems work the way they do. Stability defined in some future context may be the outcome (warm Earth, oceans 60+ m higher), but the process may be comparable to being a cork in a whirlpool once initiated.

    So I think what we’re doing is also significant on the geological scale.

  11. Therein lieth no rub, Wozza’s Ghost, because the review process is completely transparent and described in the report. I suppose they could include denialist science in their review – only there isn’t any, is there?

  12. Roger Jones @11,

    “One fundamental property of complex self-adapting systems are feedbacks that will oscillate due to internal and external forcing. The same properties that make them self-adapting, also produce large perturbations if subject to rapid changes in energy inputs.”

    That is the sort of answer I am looking for, although I don’t quite understand it. Do you have any good references?

  13. Wozza’s Ghost, climate science is not just the models, it includes the empirical observations that show the planet is warming (Nick Minchin notwithstanding).

  14. WG @9,

    I wasn’t saying that I agree with Hansen (in fact, I don’t know enough about the science to have any view on whether he is right or wrong), I was just using his positions to help to elucidate the question I am asking.

  15. Ah, sg, the old “denialist” gambit, well done. Didn’t take long either – run out of facts even earlier than usual did you?

    Look, I don’t want to derail this thread which is potentially a very useful one. Perhaps you do. So I will just say that the IPCC uses a particular suite of models, selected to certain criteria. The selectivity and the criteria are the issue. Go read about it, and stop trying to change the subject and/or shout abuse.

    Unless you have something useful to say on the actual question of feedbacks?

    No, thought not.

  16. WG,

    The models are part of the CMIP program run by the World Climate Research Program, where the basic schemes (atmosphere, ocean, land surface, chemistry) are decided by scientific meeting. All modelling groups are invited to submit and all submissions that meet the experimental criteria are analysed. All submitted data are downloadable. Scientists designing experiments – outrageous!

    Cite for Hansen in 1986 please. He wasn’t saying that in 1988 to congress. See Fig 2.3.

    Lindzen and Choi might not be a good paper to cite. They make an error in a key equation, and try to infer global climate sensitivity by looking at the top of atmosphere radiation and temperature in part of the tropics, avoiding heat transport to other latitudes and into the ocean.

    The evidence that sensitivity is positive is comprehensive. You infer that the weaknesses in the climate models invalidate their use. That’s your opinion and overlooks the scientific literature on the subject.

  17. Wozza’s Ghost, you have presented anything resembling a fact in years. You start the conversation with the old “computer modelling” furphy and accuse me of a gambit? Cheap!

  18. Roger Jones,

    OK, let me see if I understand. The climate, per se, is not adaptive (air and water molecules are just molecules, they don’t change behaviour) so you must be referring to eco-systems. Yes?

    So, is it that rapid changes to forcing do not allow time for ecosystems to respond in a “negative feedback” sense and they may, instead, respond in a “positive feedback” sense? For example, instead of trees growing bigger, they just die off.

    That principle may explain ecological feedback, but it does not seem to explain inorganic positive feedback: eg clouds.

    Or am I missing the point?

  19. I&U,

    the climate system can be said to be adaptive according to definitions of complex adaptive systems. Part can be biological, but physical aspects can also be adaptive if internal processes (feedbacks and such) modify the behaviour of the system. Self-regulation in complex systems is called adaptive behaviour according to that definition.

    Clouds are a really good example to show local and regional feedback. In the tropics, high evaporation leads to large uplift, cloud formation and rain, leading to cooling through the latent heat of evaporation. Higher global temperatures lead to increased equator to pole movement of heat, that leads to long-term polar warming.

    Self-regulating behaviour in economies led Adam Smith to coin the term ‘invisible hand’ because it seemed that markets were internally guided. Like phenomena are now being recognised in a wide range of systems. They don’t have any moral force or internal purpose, they just are.

    Most complex systems are buffered in some way by a combination of fast and slow feedbacks. If too much energy is put into a system too quickly it may shift to more chaotic behaviour or experience a threshold shift that signals a new set of behaviours. The fast processes dominate.

    Forcing can produce a very different state. Your tree argument is a good one – vegetation thresholds are very strong, drought may cause collapse of a significant forest region, removing it as moisture source and producing a long-term shift to savannah. Shifts in subsiding, dry tropical air moving over a forested region could do this, for example.

    The technical aspects of the linked discussion paper, if you can follow it (and overlook the policy arguments for the purpose of following the scientific argument), lays it out really well. The two biggest positive forcings are water vapour and land albedo. Clouds can be thought of as a regulator.

    The question is how active or passive clouds are as a feedback in limiting this positive forcing. Lindzen argues they are a strong negative feedback at the global scale but has never produced a compelling argument. Most think of clouds as fairly passive, although locally they are important. I think if Lindzen’s argument had any legs, we’d be seeing something measureable.

    In some regions, cloudiness is decreasing as rainfall increases, because of changes to cloud types, as cumulus types become more common.

    The addition of long-term positive forcing into the scientific debate on climate change has a lot of support from palaeoclimatic evidence, ice melt especially. The really long feedbacks, geochemical processes involved in the carbonate cycle, take even longer to play out.

  20. Great post again Brian

    Brian wrote: BTW Hansen thinks that Gaia as a factor that intentionally steers the system towards conditions suitable for life is basically rubbish. The earth system doesn’t care whether we turn into a Venus-like planet.

    I understand you’re putting Hansen’s position here

    For arguments sake, it seems to me if you’re to include living things as an integral element of the Gaia hypothesis, which it is I figured. Then there’s certainly evidence that life from the microbial upwards, almost by definition, alters the environment to facilitate suitable conditions within any available thermal and chemical opportunities or limitations. At least for it’s circumstance and type.
    Living things would probably somehow try to mitigate against an inhospitable Venus earth scenario if it could develop. Or adapt?

    Do plants and algae care about the oxygen that they make that permanently altered the gases in the earth’s atmosphere? That facilitates the entire biota of higher animals?
    Why is there such a basic and deep complementarity between the major classes of living things on planet earth?
    Isn’t there much evidence for how fungus, plants, worms and insects turn over vast quantities of materials globally and modulate the atmosphere and climate locally and globally?

    Actually I just found this interesting page at the American Institute of Physics site on exactly this point.

    Living things seem the most obvious force towards creating conditions suitable for life generally to me.
    Guess an answer could depend on someone’s definition of what is life? and what is meant by intention?

    I&U wrote: Now, if you were driving your car and increased the gas by 1%, you wouldn’t expect your engine to explode. Rather, your car would speed up by 1% (or 0.5% is it?).

    The way I see it is to think of it more like 1% increase per minute for a mechanistic car metaphor. Which left to continue will see your engine go past its working range and possibly explode. If you didn’t slam into something first.

  21. Brian: Really interesting post. Nicely lays out everything about the ‘climate always changes’ lie.

    Just a couple of comments/questions. Firstly, how much of the variation in the last 3 million years (in your figure 5) is due to actual variation, and how much is just due to the fact that we have a much more detailed record?

    Also, you say

    The greenhouse gases, … give us an extra 32C or so and equalises the temperature across the 24 hours and the seasons.

    but you’ve forgotten the oceans here! They’re far more important than the atmosphere in moderating seasons and day/night temperatures. Maybe it’s just being around oceanographers too much 🙂

    I suspect atmospheric heating will just be the tip of the iceberg. Oceanic heating is pretty key. I still disagree about whether we could turn into Venus – you’d have to boil off all the oceans first and that should be pretty hard I would imagine. Not that a 6 degree increase in the global temperature would be a walk in the park by any means.

  22. Brian

    Useful post, but some of the terminilogy is wrong.

    First up, it’s forcings that change the temperature positively or negatively. Forcings are amplified by feedbacks, positive and negative. For a stable climate the net effect of forcings and feedbacks should be zero, they should cancel each other out.

    This isn’t correct. A change in forcing will change temperature positively or negatively. Forcings are amplified by positive feedbacks, and reduced by negative feedbacks. For a stable climate, we need stable forcings and no positive feedback

  23. P.S. I can see how this mistake can occur. If we define a forcing such that a positive change in forcing makes things hotter, and a negative change in forcing makes things colder, it might be inferred that a positive feedback also makes things hotter and a negative feedback makes things colder.

    But that’s not how the term “feedback” is defined. Positive feedback amplifies the change in forcing, in whichever direction, and negative feedback reduces it, in whatever direction.

    The non-intuitive part, though, is that a system that only has negative feedback will be stable, whereas a system that has any positive feedback at all will be unstable.

    The sentence above is universally true. Most systems are non-linear, so that a positive feedback will ultimately turn negative, but as long as there is a positive feedback present, the system will be unstable.

  24. @SJ:
    “The non-intuitive part, though, is that a system that only has negative feedback will be stable, whereas a system that has any positive feedback at all will be unstable.”

    This is not always true. Negative feedback can lead to dynamic instability, i.e., larger and larger oscillations, if the response of a system is slow enough so the feedback signal is out of phase with the input signal and thus amplifies it, even though, being “negative”, it is in the opposite direction to the input that caused it.

    I don’t think this is significant for the sort of climate change we’re discussing though. Possibly something of the sort is probably behind the Southern Oscillation and the sun-spot cycle — I don’t think anyone knows for sure. Both of these occur on a time scale significantly faster than anthropogenic global warming and so are pretty much independent of it, though they confuse the signal enough to provide talking points for the denialists.

    The other big oscillatory phenomenon of the last couple of million years, the earth passing in and out of ice ages, seems to be more of a limit cycle, which unlike feedback instability is due to the system being highly nonlinear, leading to it flipping from one state to another, regulated, but not driven, by orbital fluctuations.

    What you say about positive feedback is basically correct.

  25. SJ, I see what you say. My understanding of science is quite limited and sometimes it shows.

    Quoll @ 24, I was taking a bit of a shortcut with Hansen on Gaia. What he actually said in the Bjerknes Lecture was the following:

    How does the Earth manage to stay in this habitable range? Is there a Gaia phenomenon keeping the climate in bounds? A nice idea, but it doesn’t work.

    The Earth’s climate becomes more sensitive as it becomes very cold, when an amplifying feedback, the surface albedo, can cause a runaway snowball Earth, with ice and snow forming all the way to the equator.

    If the planet gets too warm, the water vapor feedback can cause a runaway greenhouse effect. The ocean boils into the atmosphere and life is extinguished.

    The Earth has fell off the wagon several times in the cold direction, ice and snow reaching all the way to the equator. Earth can escape from snowball conditions because weathering slows down, and CO2 accumulates in the air until there is enough to melt the ice and snow rapidly, as the feedbacks work in the opposite direction. The last snowball Earth occurred about 640 million years ago.

    Now the danger that we face is the Venus syndrome. There is no escape from the Venus Syndrome. Venus will never have oceans again.

    Or in my words, climate sensitivity is not a universal constant. At a certain point at the cold end of things you get runaway conditions that could lead to snowball earth. There is a way back from there.

    But at the hot end of the spectrum there is also a tipping point, from which there is no way back.

    Then he says this:

    Given the solar constant that we have today, how large a forcing must be maintained to cause runaway global warming? Our model blows up before the oceans boil, but it suggests that perhaps runaway conditions could occur with added forcing as small as 10-20 W/m2.

    10-20 W/m2 on top of 340 isn’t all that much.

  26. IU @ 6 and elsewhere, I’m glad Roger was around to help.

    Your comment on the other thread set my mind working on some stuff I’d been thinking about from time to time. In the end I used it as a hook for this post. So I’m sorry for the misunderstanding but it may have been a productive one and may have incidentally helped you down the track you wanted to go.

  27. Living things seem the most obvious force towards creating conditions suitable for life generally to me.
    Guess an answer could depend on someone’s definition of what is life? and what is meant by intention?

    Just a quick drive-by here Quoll, but there’s no need for “intention” if you take an evolutionary perspective. The life-forms most likely to survive are the life-forms that (as a happy by-product of their metabolic processes) just happene to produce micro- or macro-climates most conducive to their survival.

    To put it another way, anywhere you find life in the universe, you should expect to find a “Gaia”-like situation: because any life-forms that don’t produce a “Gaia”-like stasis simply don’t survive long enough — along comes the first solar flare or ‘snowball’ earth, and it’s curtains…

  28. Nice presentation Brian. I think that the barrier between where we are an the venus syndrome is total cloud cover. So the bottom end is snow ball earth and the top end is cloud ball earth. Either is the end of most life.

    OT. In some countries they just get on with things, just get on with being clever and making things better.

    When we get past this almost endless argument about Climate Change and sack the ratbags who are feeding it, we too will discover that facing up to change leads to a better way of doing things. And there are so many improvements to be made, while preserving the beauty of the natural world.

  29. Brian, Roger, Quoll, Mercurius et al.

    Quoll’s ecological/evolutionary argument and Mercurius’s use of the anthropic principle both make sense to me and would explain why the earth’s climate is likely to be robust against changes and rates of changes in forcings comparable to historical levels. Thus, Brian’s presentation demonstrating that the rate of change of forcing is very different to historical experience is very significant.

    Roger’s argument that the climate itself is an adaptive system is harder for me to get my head around and I shall read the paper he linked to with interest.

    Overall, a very useful and interesting thread. Thanks.

  30. I&U,

    because I have to run and am already late … Quoll’s, Mercurius’ and my points are all related.

    The key point is that these systems aren’t mechanistic. Because they are complex there is quite a bit of different but related language and metaphor used to describe them. For instance, the anthropic principle suggests that the invisible hand of economics just is,and has no intrinsic purpose.

  31. This is not always true. Negative feedback can lead to dynamic instability, i.e., larger and larger oscillations, if the response of a system is slow enough so the feedback signal is out of phase with the input signal and thus amplifies it, even though, being “negative”, it is in the opposite direction to the input that caused it.

    Huh? “Negative” means negative and “out of phase” also means negative. -1 x -1 = +1. Your feedback here is actually positive.

    Let’s put it another way: If the linearised state equations have any eigenvalues with positive real parts, there is positive feedback present, and the system is unstable. If any of the eigenvalues have non-zero imaginary parts, there will be oscillation in response to any peterbation, but stability is determined solely by the real parts of the eigenvalues.

  32. SJ, in this case “negative” means that the effect of the feedback is to lower temperature. Seems quite straightforward to me.

    BilB @ 32, the notion of cloud-ball earth is intriguing. You should tell Dr Hansen. Maybe he overlooked that possibility 🙂

  33. Merc @ 31 makes sense to me.

    My understanding of Lovelock’s Gaia insight was initially that organisms don’t just live within an inorganic system, they change the inorganic system in a way that is pro-life. So success biologically will give the impression of intent in the system.

    Gaia is actually a feature of successful life, which is what I think Quoll was saying.

    On definitions of “intention” it implies to me a choice among alternatives, which is only possible with human brain power. I guess it is possible to speak of a pro-life force in all living things, or the old psychological term “drive” which you don’t see much these days.

  34. Wozza @ 7, I was going to leave your constant bringing up of contrarian talking points from the denialosphere go through to the keeper, as it was answered by Roger @ 20.

    My attitude to Lindzen is that if you wait long enough a climate scientist will come along and show where he’s wrong. Happens every time, except sometimes climate scientists are busy elsewhere and then it stands.

    This is not a climate science blog in that sense. I don’t welcome contributions of that ilk and would ask you to take them to deltoid or a site that specialises in arguing with socalled skeptics.

    Hansen in Storms of my grandchildren says that Lindzen made a reputation “primarily as a result of brilliant mathematical analyses of atmospheric dynamics.” Unfortunately he is emotionally attached to the notion that humans don’t have much impact on the atmosphere, so, Hansen says, his current work is largely not scientific. Rather he looks only for evidence that supports his preconceived views, as a lawyer looks for arguments to defend a client.

  35. Brian @36,

    Cloud ball earth is what killed off the dinosaurs (according to the theory) but in that case it was triggered by a massive meteor strike. The result was a surface winter (nuclear winter). So what I am guessing is that if the oceans heat up enough this would cause ever increasing cloud cover to the point that a cooling effect set in. Though this cooling effect takes a hundred thousand years to reverse the process of warming to a cooling, according to the research on extinctions that is, as the heat can only escape slowly. That is my guess, so I don’t think that the Venus syndrome can occur for Earth till the Sun expands a little more. I imagine that on heading towards a cloudball Earth would be a wild ride for the surface as it would be a world of massive rainfall, super ferocious winds and perpetual lightning.

  36. Brian @37, yes Lovelock’s insight was that organisms become significant positive/negative climate feedback mechanisms in their own right. Plus they can often impact far faster and more cyclically than geological ones.

    A (very) simple conceptional example would be vegetation, growing and taking CO2 out of the atmosphere. This starts to create a cooling effect, which along with the lower CO2 creates a die off effect. The rotting vegetation gives off CO2 and methane and the climate heats and growth rates increase again.

    This means a far more cyclic and shorter climate cycle imposed upon any other longer term geological/solar/orbital/etc impacts. Under certain conditions this can moderate the ‘mega’ cycles, creating a more stable system.

    Note that life on the land seems to able to handle large climate changes provided they are slowly emerging, cyclical and with sufficiently large land masses for migration.

    The recent period of glacial/inter-glacial, though it has large swings in climate, is still a very stable cycle, with plenty of time for migration and adaption. The impact of organisms seem to be a significant factor in these cycles.

  37. Brian @ 38 My understanding of Lindzen’s claims about cloud albedo effects was that he made those based on models which didn’t have any coupling between the atmosphere and the ocean. When his simulations were re-run on a fully coupled model the albedo feedback not only disappeared, it even changed sign the other way. Roger probably knows more about this than me though.

    I’ve also heard on the grapevine that he gets his errors regularly pointed out to him, and even goes as far as saying that he’s wrong, but two months later starts spouting the same incorrect crap. It’s mind-boggling really, but I suppose it’s a case of Kuhn’s model of science – we have to wait until all the old scientists are dead before we can move on properly.

  38. Jess, this is part of what Hansen says about Lindzen’s ideas on climate sensitivity. Lindzen had proposed:

    a specific mechanism for how the atmosphere takes care of itself. He suggests that columns of tropical convection intensify if carbon dioxide increases, piping energy high into the atmosphere, where heat would be radiated to space.. This mechanism, he suggests, is nature’s thermostat, which keeps global warming to a few tenths of a degree for doubled carbon dioxide, rather than a few degrees.

    Seems highly implausible and Hansen says the paleorecord shows clearly that he is wrong. But

    I expect him to keep asserting that human-made climate change is unimportant on his deathbed, defending it as a lawyer seeks to win for a client.

    Hansen reckons he is always calm and self-assured personally and communicates authority nonverbally, as it were. But that didn’t stop him in from indulging in essentially a barefaced lie that made Hansen look stupid when they both were called to see Dick Cheney.

    I have limited time to spend on reading about climate change and don’t have time to keep chasing that rabbit down a hole.

  39. BilB @ 39, my understanding is that high thin clouds stop more outgoing than incoming radiation and so have a warming effect. Low thick clouds have the opposite effect. So where you get more or less of which type of cloud determines the net effect.

    Hansen says his model blew up as it approached extreme conditions and I understand that we still have much to learn about cloud formation.

    So the bottom line is that we don’t know, but generally it is not smart to bet against Hansen’s best guess.

  40. It is safe to speculate from my position (and speculate I will) on this particular outcome as we will never get to that point, so we will never know for sure, cerainly not in my lifetime. Point taken on the cloud layers, we will certainly be getting some real world idea on what sort of clouds form from increased ocean temperatures over the next 30 years. It is important though as cloud cover affects solar energy performance.

  41. A marvellous synthesis Brian,comprehensible for the lay person. Your posts make this site an essential resource. This sort of work should be constantly in the mass media, that it is not is very worrying.Unusually instructive wikipedia like posts as well!
    I have poor health so it can be a struggle to keep up to date and grasp of overall climate trouble data. Thanks for your work, it helps provide framework for my own in different field.

  42. Brian @42,

    spot on. These speculations from Lindzen ignore palaeoclimate. Lindzen has had two bites at the cherry with the Iris effect and most recently with the top of atmosphere energy balance in the tropics. Both have been tested and found seriously wanting.

  43. Brian @ 38

    Having said my piece I wasn’t going to weigh again either. I know how futile it is to continue to argue anything contrary to the fixed beliefs of the majority on this blog, even by referencing a peer-reviewed paper.

    However, if your view is that “this is not a science blog” of the sort in which people can actually point to scientific papers, why do you bother parading selected quotes from science at all? Because they support a view that you have fixed on for reasons unrelated to science is about the only conclusion one can draw. Especially when you say that the reason you ignore Lindzen is that you assume that someone will refute him eventually, and Hansen has come out with some critical views on Lindzen’s personality.

    Look, as I have said before in the context of the regular lists of cherry-picked mishmash which constitute the Climate Clippings, it is your blog. You can write what you like, and I will if you wish refrain in future from making any comment at all on it. But don’t be under the illusion that by doing so – that is, presenting only stuff carefully selected to a briadly pre-determined conclusion – you are making any contribution whatsoever to a rational discussion of things climate. You are providing a comfort blanket for the many on this blog who also have a fixed view of the subject which they would prefer not disturbed by news at variance with that view.

    This may be a desirable public service, of course.

    Roger @ 20. Hansen’s 1986 statement reported here:

    For the record, I did not infer (or imply) that “the weaknesses in the climate models invalidate their use”. I specifically acknowledged that the modelling is useful, but needs to be interpreted in the light of the fact that it has now been out of line with the actual temperature increase record for at least a decade – not proof of anything, but increasingly suggestive as time continues to go by with this trend unchanged. The issue is about risk management – the risk that the modelling is overstating the problem needs to be factored into decision-making. That is all I am saying.

    I would be interested in a reference to the “comprehensive evidence” that sensitivity is positive, rather than the simple argument from authority. The question, again, is how positive.

  44. Wozza, I see my role as a citizen journalist. I’m not qualified as a scientist. Ultimately my interest is in policy. So when I look at the science I try to make it more accessible for people who have an interest in public policy on climate change, and who vote.

    I’m certainly interested in science that departs from the norm. Hansen’s view that climate sensitivity should be doubled from a midpoint of 3C to 6C was one such example.

    I’m not taking that as gospel, BTW, but his notion that long-term feedbacks will get you to a figure significantly above what had been considered the norm clearly has merit. His view has received some support in studies on the Pliocene by Lunt et al and again by Pagan et al. These are the kind of articles I would draw to peoples attention in Climate Clippings if I were doing it at the time.

    I didn’t, however, include this one on the Lindzen-Choi paper, because the Lindzen-Choi paper is clearly crap and posting about it is an invitation to waste thread-space talking about it.

    How do I know it’s crap, not being a scientist? Well Lindzen usually is, but anyone can see that Tom Wigley has a point:

    You say “LC09 was not a nonsense paper – that is, it didn’t have completely obvious flaws that should have been caught by peer review “. I beg to differ.

    It is a priori obvious that one cannot determine the climate sensitivity from an incomplete energy balance over the tropics. LC09 ignores the fluxes of heat into and/or out of the region via the atmosphere, and the flux of heat into the ocean. As Trenberth et al. point out, these are large terms, and they simply cannot be ignored. This is a glaringly obvious error that any competent reviewer should have picked up. It undermines the whole analysis and makes it worthless. In my view, the other issues raised by Trenberth et al. are important, but secondary to this fundamental problem.

    If you want to argue the toss using Lindzen it’s more appropriate that you do so on that thread at Climate Progress or this one at Skeptical Science.

    On climate sensitivity, did I use the phrase “comprehensive evidence”? Apart from the Skeptical Science link I did refer in the post to Hansen’s Bjerknes Lecture. I’m sure there is an instructive slab on the topic in the IPCC AR4. It was central in Morgan and McCrystal’s Poles Apart where they ultimately found the sceptics’ position wanting. They have a useful section on the nature of models and their use in climate science, BTW.

  45. I know how futile it is to continue to argue anything contrary to the fixed beliefs of the majority on this blog, even by referencing a peer-reviewed paper.

    Wozza, when the paper you refer to is by Lindzen, you can’t really expect anyone to take you seriously.

    I think you’ll find, also, that the beliefs of the majority on this site are: a) not fixed; b) informed by extremely rigorous science; and c) suppported by more facts than you can poke a stick at.

    It seems to me that you are merely a contrarian (or perhaps captured by ideology), rather than a genuine sceptic.

  46. Wozza,

    You seem to be cherry picking too. It’s just that you have far fewer cherries to choose from.

    Why are you citing Lindzen? Do you consider him a more credible scientist that those cited by Brian and others? Do his findings support your prejudices? Or are you just being contrarian?

  47. DI(nr) @ 49, I think our commenters in general have a pretty good grasp on climate science and are unlikely to be distracted by Wozza’s advocacy of Lindzen. It’s the lurkers I worry about.

    The blog stats suggest that for every commenter there are multiples of lurkers who don’t comment. There is no way of knowing what their level of knowledge is.

  48. Well there you go, MTS, Muller has a good approach. Drown people in numbers. I’ll wait for the expert analysis from the scientists at large, and the statisticians. In between time I make judgements based on my accumulated knowledge and on my intuition. I never take any information source for granted, always seeking correlation from credible sources. Carry on.

  49. call me a cynic, if you will, but Muller’s project reeks of arrogant physicist syndrome: he thinks he is so good at numbers that he can just waltz into someone else’s highly complex field and “correct” their “errors.” I predict his work will show nothing new, will be politicized just as much as everyone else’s and will change nothing.

  50. SJ @35:
    We’re in complete agreement as to what happens in a (linear) system with feedback. I don’t see any point in arguing definitions, so I’ll just reword what I said thus: “A feedback which would oppose the input if it remained constant can lead to oscillatory instability if it’s sufficiently large and there’s sufficient delay in the system.”

    Anyway, as I said, that doesn’t happen in the climate system on the time scales relevant to AGW, so it’s off-topic wrt this thread. So I’ll shut up.

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